Fluorescent lamp with low melting amalgam filling



06L 1964 H. DZIERGWA ETAL 3,152,278

FLUORESCENT LAMP WITH LOW MELTiENG .AMALGAM FILLI NG Filed May 31, 1960 TO VACUUM SOURCE FROM COM- PRESSED GAS SUPPLY Fig. 2

Fig.3

INVENTO RS United States Patent 3,152,278 FLUORESCENT LAMP WITH LOW MELTING AMALGAM FILLING Herbert Daiergwa, Eerlin-Nikolassee, Lothar Busch,

Eerlin-Wilmersdorl, and Kathe Ristau, Berlin-Schlachtenses, Germany, assignors to Pateuh'lreuhand Gesellschaift fiir elelrtrische Gliihlainpen m.b.H., Munich, Germany Filed May 31, 196%, Ser- No. 31,782 Claims priority, application Germany June 12, 1959 3 Claims. (Cl. 313-174) The present invention relates to high output and highly loaded fluorescent lamps, and more particularly, to an improved high output and highly loaded fluorescent lamp and a method of and apparatus for manufacturing same.

it is well known in the manufacture of high output and highly loaded fluorescent lamps that the most efficient operation of such lamps is obtained at a mercury vapor pressure of about 6-10 microns, namely the vapor pressure of mercury between 40 C. and 45 C. When such fluorescent lamps are lighted, the bulb Wall temperature increases towards its equilibrium value of 85 C. to 90 C. with an attendant mercury vapor pressure increase which exceeds the 6-10 microns of mercury vapor pressure deemed best for maximum efiiciency of the generation of 2537 radiation, thus resulting in a reduced amount of emitted light. Unless a cool spot is provided within the lamp at a temperature of about 40 C. such lamp will continue to operate inetliciently.

it is an object or" the present invention to provide an improved high output highly loaded fluorescent lamp having its maximum efficiency for the generation of mercury resonance radiation at higher lamp temperatures than in conventional high output highly loaded fluorescent lamps.

Another object of the present invention is to provide a method for depositing a compact body of the present invention on the envelope of the improved high output highly loaded fluorescent lamp.

A further object of the present invention is the provision of an apparatus for depositing the compact body of the present invention on the envelope of the high output highly loaded fluorescent lamp.

The aforesaid objects of the present invention, and other objects which will become apparent as the description proceeds are achieved by providing such high out put highly loaded fluorescent lamp with a mixture, combination of an amalgam or an amalgam-forming metal, such as cadmium or indium, and one or several metals of low melting point, eg. gallium, soft-solder without or with gallium or the like. By soft-solder it is intended to signify preferably an alloy of tin, lead, cadmium and bismuth. Another proposal according to the invention consists in that the amalgam or one of its components should be mixed with an adherence-favouring substance, cg. an inorganic binder as a glass frit or enamel containing lead borate.

The method of the present invention comprises the steps of removing a portion of the phosphor coating from the lamp envelope, heating the compact body to plasticity and propelling and pressing the plasticized compact body against the cleaned portion of the lamp envelope. The apparatus for applying the compact body to the high output highly loaded fluorescent lamp comprises a suction device for removing a portion of the phosphor coating from the envelope wall and a depositing device having means for heating the compact body to plasticity and pneumatic means for directing the plasticized compact body into contact with the cleaned portion of the lamp envelope.

For a better understanding of the present invention,

eterence should be had to the accompanying drawing,

3,152,278 Patented Oct. 6, 1964 wherein like reference numerals indicate similar parts throughout the several views and wherein:

MG. 1 is a diagrammatic side-elevational view, partly in section, of a suction device for removing a portion of the phosphor on the inner surface of a high output highly loaded fluorescent lamp envelope preparatory to the deposition of the compact body thereon.

FIG. 2 is a diagrammatic side-elevational view, also partly in section, of a depositing device for attaching the compact body to the now cleaned inner surface of the fluorescent lamp envelope.

FIG. 3 shows a generally conventional fluorescent lamp envelope except for a section cut open to illustrate the compact amalgam forming body according to the invention.

With specific reference to the form of the present invention illustrated in the drawings and referring particularly to FIGS. 1 and 2 a compact body of the present invention is indicated generally by the reference numeral 4.

This compact body comprises a mixture or combination of a pulverulent amalgam-forming metal, such as cadmium and indium, and one or several low melting point metals, such as gallium or soft-solder and/ or an adherence-favouring substance, e.g. an inorganic binder as an enamel or glass frit containing lead borate.

As a specific example, such compact body may comprise, for example, one part by weight of cadmium powder, one part by Weight of mercury and three parts by weight of a soft-solder powder, an alloy of lead, tin, bismuth and cadmium. Such mixture or combination of the above-mentioned elements is compacted or sintered into a compact body having a small volume relative to its surface area; as illustrated, it may be formed into a disc-like or cylindrical tablet having a diameter of about 6 mm. and a thickness of 1 mm. The compact body 4 may also be formed into rectangular solid shapes such as cubes and the like.

Referring to FIG. 2, it will be understood that when an envelope 1 orthe high output highly loaded fluorescent lamp (not shown) carries a phosphor 2, the suction device shown in FIG. 1 is utilized first. Such suction device comprises a tube it) having an angularly or laterally extending portion 12, and a pivotable connection 13 for permitting the rotation of the angularly extending portion l2 into contact with a portion of the envelope 1 from which the phosphor 2 is to be removed. The diameter of the angularly extending portion 12 is a little larger than the diameter of the compact body 4. Such tube lift is connected through a vacuum valve 11 to a vacuum source (not shown) but indicated in FIG. 1 by the direction arrow and the legend to to vacuum source. By means of the pivotable connection 13, the angularly extending portion i2 is pressed into contact with the inner surface of the envelope It to permit the sucking-oil of the phosphor 2 at the contact area.

The suction device is then retracted preparatory to the depositing operation associated with the compact body 4.

This compact body t is then loaded into a recess 6 provided in a laterally or angularly extending portion 14 of a metal tube 5, which metal tube 5 is connected by means of a heat insulating intermediate portion 7 to a pivotable connection 16. Additionally, the metal tube 5 extends through a throttle valve 8 and a pressure-reducing valve to a compressed inert gas supply (not shown) but indicated by the direction arrow in FIG. 2 and the legend from compressed gas supply.

Such compact body 4 is heated by means of an adjustable electrical heating means, such as the heating coil 15, to partial or complete plasticity as desired. The angularly extending portion 14 is then moved by means (of pivotable connection 16) into contact with the now greases cleaned portion of the lamp envelope (FIG. 2) to dispose the now plastic compact body adjacent such now cleaned portion of the lamp envelope 1. Compressed air or preferably an inert gas which does not react with the compact body 4, such as nitrogen, is then introduced under pressure through pressure reducing valve 9, throttle valve ti, metal tube and angularly extending portion 14 to propel or press the plasticized compact body against the now cleaned portion of the envelope 1. Thereafter the depositing device is retracted from the lamp envelope. The compact body 4 is shown adhering to the envelope wall in FIG. 3.

During the heating of the fluorescent lamp (not shown) and the exhausting thereof, the compact body 4 may be maintained below its softening temperature by directing a blast of cool air against the portion of the envelope 1 carrying the compact body It will be understood by those skilled in the art that the tube 5 may be connected by conventional means, such as a valve and T-connector (not shown) to the vacuum valve 11 and the vacuum source thus incorporating the suction device in the depositing device.

The improved etliciency of the hi h output highly loaded fluorescent lamps at higher operating temperatures is obtained in the following manner.

With amalgam present in the discharge envelope the mercury vapor pressure of the lamp is lower than the mercury vapor pressure in lamps containing free mercury without amalgams at like temperature and, therefore, provides an increased radiation output or the mercury resonance radiation. Thereby, the optimum of radiation output of the mercury resonance radiation in comparison to lamps lacking amalgam-forming metals is shifted towards higher lamp temperatures and only achieved with higher input. The deposition of the amalgam in the lamp in form of a compact body is highly advantageous in that the heating and exhausting process of lamps containing amalgam hardly differs from that of conventional lamps since it is easily possible to keep the small area of amalgam-deposition cool, i.e. below the softening temperature of the compact body, for instance by a blast of air.

It will be recognized by those skilled in the art that the objects of the present invention have been achieved by providing an improved high output highly loaded fluorescent lamp which will operate elhciently at high lamp temperatures by providing such fluorescent lamp with a compact body comprising an amalgam of mercury and a low melting point metal or metals. A method of and apparatus for applying such compact body to the 4- high output highly loaded fluorescent lamp has also been provided.

While in accordance With the patent statutes one best known embodiment of the present invention has been illustrated and described in detail, it is to be particularly understood that the invention is not limited thereto or thereby.

We claim:

1. In a hi h output highly loaded fluorescent lamp comprising a vitreous envelope containing an ionizable medium including mercury and wherein mercury vapor at a pressure in the range of 6 to 10 microns corresponding to a temperature range of to C. is optimum for generation of 2537 A. radiation but wherein an envelope Wall temperature in excess of said temperature range as a result of high loading would entail a vapor pressure exceeding said optimum range, a compact body having a small surface area relative to its volume ait'ixed internally to the wall of said envelope and covering only a minor portion of the circumference thereof, said compact body comprising a metal forming an amalgam with mercury and a low melting point metal and being adapted, at said envelope wall temperature, to lower the mercury vapor pressure within said envelope towards said optimum range.

2. A lamp as defined in claim 1 wherein the compact body comprises, for the metal forming an amalgam with mercury, a metal selected from the group consisting of cadmium and indium and alloys thereof, and for the low melting point metal, a metal selected from the group consisting of gallium, lead, tin, bismuth and cadmium and alloys thereof.

3. A lamp as defined in claim 1 wherein the compact body comprises, for the metal forming an amalgam with mercury, a metal se ected from the group consisting of cadmium and indium and alloys thereof, for the low meling point metal, a metal selected from the group consisting of gallium, lead, tin, bismuth and cadmium and alloys thereof, and further comprises an adherence-favoring substance in the form of an inorganic binder containing lead borate.

References Cited in the file of this patent UNITED STATES PATENTS 1,971,945 Winninghoff Aug. 28, 1934 2,449,637 Blake et al Sept. 21, 1948 2,450,197 Ishler Sept. 28, 1948 2,476,681 Overbeek et al July 17, 1949 2,491,854 Force Dec. 20, 1949 2,879,583 Booth Mar. 31, 1959 3,007,071 Lompe et al Oct. 31, 1961 

1. IN A HIGH OUTPUT HIGHLY LOADED FLUORESCENT LAMP COMPRISING A VITREOUS ENVELOPE CONTAINING AN IONIZABLE MEDIUM INCLUDING MERCURY AND WHEREIN MERCURY VAPOR AT A PRESSURE IN THE RANGE OF 6 TO 10 MICRONS CORRESPONDING TO A TEMPERATURE RANGE OF 40 TO 45* C. IS OPTIMUM FOR GENERATION OF 2537 A. RADIATION BUT WHEREIN AN ENVELOPE WALL TEMPERATURE IN EXCESS OF SAID TEMPERATURE RANGE AS A RESULT OF HIGH LOADING WOULD ENTAIL A VAPOR PRESSURE EXCEEDING SAID OPTIMUM RANGE, A COMPACT BODY HAVING A SMALL SURFACE AREA RELATIVE TO ITS VOLUME AFFIXED INTERNALLY TO THE WALL OF SAID ENVELOPE AND COVERING ONLY A MINOR PORTION OF THE CIRCUMFERENCE THEREOF, SAID COMPACT BODY COMPRISING A METAL FORMING AN AMALGAM WITH MERCURY AND A LOW MELTING POINT METAL AND BEING ADAPTED, AT SAID ENVELOPE WALL TEMPERATURE, TO LOWER THE MERCURY VAPOR PRESSURE WITHIN SAID ENVELOPE TOWARDS SAID OPTIMUM RANGE. 